The synthesis of aqueous MPA-capped CdTe quantum dots (QDs) via a facile one-pot route was developed. The particle size, optical properties and crystal structure of the as-synthesis QDs were investigated by transmission electron microscopy (TEM), Fourier transform infrared (FTIR), UV-vis absorption and photoluminescence (PL) spectra, respectively. Meanwhile, the effect of reaction conditions, including reaction time, pH and the quantity of sodium citrate (SC) on the growth of CdTe QDs were discussed. Then, the obtained CdTe QDs were successfully used for the detection of trace Cu2+ with high sensitivity and excellent selectivity. The fluorescence intensity of CdTe QDs with Cu2+ concentration showed a linear relationship in the range from 1 x 10 -7 mol/L to 1 x 10 -6 mol/L. The correlation coefficient (R) is 0.9980 and limit of detection (LOD) is 1.0 x 10 -8 mol/L. Moreover, the concentration of Cu2+ in tap water samples was determined based on this sensing system and the recovery test was satisfactory.